What is "alpos"

In Nonnus' Dionysiaca (late fourth or early fifth century CE), Alpos is a Sicilian giant who terrorized Punta del Faro and he was killed by Dionysus with his thyrsus. Like the Hundred-Handed Ones he had many arms, and his head was covered with vipers, like Medusa. Alpos, who does not appear elsewhere in Greek mythology, and received no cult, may be considered an invention of the fertile imagination of Nonnus.